2015-03-31T21:03:57ZCorrespondence between Scale Morphometrics and Scale and Otolith Chemistry for Interpreting Juvenile Salmon Life Historieshttp://hdl.handle.net/1957/55454
Correspondence between Scale Morphometrics and Scale and Otolith Chemistry for Interpreting Juvenile Salmon Life Histories
Campbell, Lance A.; Bottom, Daniel L.; Volk, Eric C.; Fleming, Ian A.
Fish scales have long been used to reconstruct fine-scale habitat transitions such as the movement of juvenile fish
from freshwater, estuary, and ocean environments. Despite the importance of life history information to fisheries
management and conservation, few studies have validated that scale morphology accurately describes fish
movement between these habitats. Therefore, we tested the accuracy of using scale morphometric criteria to
identify the movement of juvenile Chinook Salmon Oncorhynchus tshawytscha from freshwater to marine portions
of the Columbia River estuary by comparing scale morphometric classification, scale chemistry, and otolith
chemistry. Nearly one-half of all fish collected in the saline portion of the estuary and approximately one-quarter in
the freshwater portion exhibited morphometric patterns (i.e., scale checks and intermediate growth) often
associated with periods of estuary rearing. Depending upon the criteria used to define scale checks, otolith chemical
results indicated that 33–53% of fish would have been misclassified as estuary residents based solely on their scale
patterns. Moreover, many individuals who had resided in strontium-rich estuary water did not form a visible check
(37%) on their scales to coincide with estuary entry. We estimated from otolith chemistry that these fish had either
entered at or near the size at which scale formation occurs (35–42 mm) or had recently migrated to the saline
portion of the estuary (<30 d) before new scale material could be formed and calcified. Scale chemistry alone was a
good indicator of entrance into the saline portion of the estuary. Scale chemistry responded to the strontium-enriched
salt water, and explained 86% of the variation found in otolith chemistry. Scale morphometric
classification did not provide the fine-scale resolution that scale and, even more so, otolith chemistry provided for
describing the proportion of juvenile Chinook salmon using the saline portion of the Columbia River estuary.
To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The article is copyrighted by the American Fisheries Society and published by Taylor & Francis. It can be found at: http://www.tandfonline.com/loi/utaf20#.VRV0PWMywS4.
2015-01-01T00:00:00ZRecovering aspen follow changing elk dynamics in Yellowstone: evidence of a trophic cascade?http://hdl.handle.net/1957/55343
Recovering aspen follow changing elk dynamics in Yellowstone: evidence of a trophic cascade?
Painter, Luke E.; Beschta, Robert L.; Larsen, Eric J.; Ripple, William J.
To investigate the extent and causes of recent quaking aspen (Populus
tremuloides) recruitment in northern Yellowstone National Park, we measured browsing
intensity and height of young aspen in 87 randomly selected aspen stands in 2012, and
compared our results to similar data collected in 1997–1998. We also examined the
relationship between aspen recovery and the distribution of Rocky Mountain elk (Cervus
elaphus) and bison (Bison bison) on the Yellowstone northern ungulate winter range, using
ungulate fecal pile densities and annual elk count data. In 1998, 90% of young aspen were
browsed and none were taller than 200 cm, the height at which aspen begin to escape from elk
browsing. In 2012, only 37% in the east and 63% in the west portions of the winter range were
browsed, and 65% of stands in the east had young aspen taller than 200 cm. Heights of young
aspen were inversely related to browsing intensity, with the least browsing and greatest heights
in the eastern portion of the range, corresponding with recent changes in elk density and
distribution. In contrast with historical elk distribution (1930s–1990s), the greatest densities of
elk recently (2006–2012) have been north of the park boundary (~5 elk/km²), and in the
western part of the range (2–4 elk/km²), with relatively few elk in the eastern portion of the
range (<2 elk/km²), even in mild winters. This redistribution of elk and decrease in density
inside the park, and overall reduction in elk numbers, explain why many aspen stands have
begun to recover. Increased predation pressure following the reintroduction of gray wolves
(Canis lupus) in 1995–1996 played a role in these changing elk population dynamics,
interacting with other influences including increased predation by bears (Ursus spp.),
competition with an expanding bison population, and shifting patterns of human land use and
hunting outside the park. The resulting new aspen recruitment is evidence of a landscape-scale
trophic cascade in which a resurgent large carnivore community, combined with other
ecological changes, has benefited aspen through effects on ungulate prey.
This is the publisher’s final pdf. The published article is copyrighted by the Ecological Society of America and can be found at: http://www.esajournals.org/loi/ecol.
2015-01-01T00:00:00ZSongbirds as sentinels of mercury in terrestrial habitats of eastern North Americahttp://hdl.handle.net/1957/55289
Songbirds as sentinels of mercury in terrestrial habitats of eastern North America
Jackson, Allyson K.; Evers, David C.; Adams, Evan M.; et al.
Mercury (Hg) is a globally distributed environmental
contaminant with a variety of deleterious effects
in fish, wildlife, and humans. Breeding songbirds may be
useful sentinels for Hg across diverse habitats because they
can be effectively sampled, have well-defined and small
territories, and can integrate pollutant exposure over time
and space. We analyzed blood total Hg concentrations from
8,446 individuals of 102 species of songbirds, sampled on
their breeding territories across 161 sites in eastern North
America [geometric mean Hg concentration = 0.25 μg/g
wet weight (ww), range < 0.01–14.60 μg/g ww]. Our
records span an important time period—the decade leading
up to implementation of the USEPA Mercury and Air
Toxics Standards, which will reduce Hg emissions from
coal-fired power plants by over 90%. Mixed-effects
modeling indicated that habitat, foraging guild, and age
were important predictors of blood Hg concentrations
across species and sites. Blood Hg concentrations in adult
invertebrate-eating songbirds were consistently higher in
wetland habitats (freshwater or estuarine) than upland
forests. Generally, adults exhibited higher blood Hg concentrations
than juveniles within each habitat type. We
used model results to examine species-specific differences
in blood Hg concentrations during this time period, identifying
potential Hg sentinels in each region and habitat
type. Our results present the most comprehensive assessment
of blood Hg concentrations in eastern songbirds to
date, and thereby provide a valuable framework for
designing and evaluating risk assessment schemes using
sentinel songbird species in the time after implementation
of the new atmospheric Hg standards.
To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Springer and can be found at: http://link.springer.com/journal/10646.
2015-03-01T00:00:00ZClimate change and vulnerability of bull trout (Salvelinus confluentus) in a fire-prone landscapehttp://hdl.handle.net/1957/55287
Climate change and vulnerability of bull trout (Salvelinus confluentus) in a fire-prone landscape
Falke, Jeffrey A.; Flitcroft, Rebecca L.; Dunham, Jason B.; McNyset, Kristina M.; Hessburg, Paul F.; Reeves, Gordon H.
Linked atmospheric and wildfire changes will complicate future management of native coldwater fishes in fire-prone
landscapes, and new approaches to management that incorporate uncertainty are needed to address this challenge. We used a
Bayesian network (BN) approach to evaluate population vulnerability of bull trout (Salvelinus confluentus) in the Wenatchee River
basin, Washington, USA, under current and future climate and fire scenarios. The BN was based on modeled estimates of
wildfire, water temperature, and physical habitat prior to, and following, simulated fires throughout the basin. We found that
bull trout population vulnerability depended on the extent to which climate effects can be at least partially offset by managing
factors such as habitat connectivity and fire size. Moreover, our analysis showed that local management can significantly reduce
the vulnerability of bull trout to climate change given appropriate management actions. Tools such as our BN that explicitly
integrate the linked nature of climate and wildfire, and incorporate uncertainty in both input data and vulnerability estimates,
will be vital in effective future management to conserve native coldwater fishes.
To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by NRC Research Press and can be found at: http://www.nrcresearchpress.com/journal/cjfas.
2015-02-01T00:00:00Z